The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in the present disclosure and are not admitted to be prior art by inclusion in this section.
Many electronic circuits, such as computer chips, use encryption keys to authenticate with another device. The encryption key is sometimes programmed by the manufacturer and stored in fuses on the electronic circuit die. However, the fuses are prone to visual and electrical probing attacks. Furthermore, since the fuses are programmed by the manufacturer, they are vulnerable to an insider attack on the test floor.
Some circuits use a physically unclonable function (PUF) circuit to generate an encryption key. The PUF circuit exploits physical variation in devices (e.g., transistors) of the PUF circuit to generate the encryption key. It is important that the PUF circuit generates a stable and repeatable encryption key. Furthermore, for high volume manufacturing of PUF circuits, it is beneficial to have high variation between different units of the PUF circuit.